Automatic air conditioning system



1937. L. L. CUNNINGHAM 2,101,308

AUTOMATIC AIR CONDITIONING SYSTEM Filed Dec. 17, 1934 OUTDOOR THERMOSTAT COOLING MOTOR Lewis L. Cunningham Patented Dec. 7, 1937 UNITED STATES AUTOMATIC AIR, CONDITIONING SYSTEM Lewis L. Cunningham, Minneapolis, Minn, as-

signor to Mlnneapo Ila-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application December 17, 1933, Serial No. 757,854 19 Claims (Cl. 236-44) The present invention relates to air conditioning systems by means of which the proper conditions are maintained within a'space to be controlled and relates particularly to the air conditioning of a space during those periods that the space requires cooling by reason of high outdoor temperatures. 1

One of the objects of the present invention is the provision of an improved air conditioning system by means of which the effective temperature of the space is varied within predetermined limits upon variations in outdoor temperature, the arrangement preferably being such that the rate of increase of the effective temperature is less than the rate of increase of outdoor dry bulb temperature. A further object of the invention is the provision of an improved system for cooling a space by means of which the dry bulb space temperature is allowed to increase as the outdoor temperature becomes progressively higher.

Another object of the invention is the provision of a control system for controlling a temperature changer in accordance with space temperature fluctuations and space relative humidity fluctuations so that a predetermined efl'ectlve temperature, or a predetermined range of effective temperature, is maintained within the space, which system has utility either during warm weather when cooling is required or during cold weather when heating is required.

Other objects of the invention will be found in the drawing, the detailed description, and the appended claims.

For a more complete understanding of the invention, reference may be had to the following description and accompanying single drawing which is a diagrammatic representation of one form of the invention.

Referring to the drawing, a temperature changer is shown at II as comprising an electric motor which may control the heating or cooling of a space in any of the usual andweli-known manners, the temperature changer II in the in- I controlled by a relay generally indicated at H.

This relay includes a relay coil |2- which, when energized, attracts an armature II that in turn moves switch arms i3 and i3 into engagement with respective contacts i3 and I1. The relay i "is'inturncontrolled by a balanced relay 23 which \includes an armature 2| havinga pair of legs 22 and 23. A pair of series connected electro- -ment with contact 3|. 1 On the other hand, if the magnetic coils 23 and 25 cooperate with the respective legs 22 and 23 of armature 2|. The armature 2| is pivoted at a point indicated at 28 and operates a pair of contact blades 21 and".

The contact blades 21 and 28 are secured to ar- 5 mature 2| through a block of electrical insulating material 29 by a rivet 30 which electrically connectscontact blades 21 and 28. Contact blade 21 cooperates with a contact 3|, and the contact blade 28 cooperates with a contact 32. The arrangement is such that when electromagnetic coils 23 and 25 are equally energized, the parts assume the position shown in the drawing wherein contact blade 21 is engaged with contact 3|, but contact blade 28 is disengaged from contact 32. If the electromagnetic coil 23 becomes more highly energized'than the electromagnetic coil 25, the contact blade 21 is moved from engageelectromagnetic coil 25 becomes more highly energized than the electromagnetic coil 23 by a predetermined amount, then contact blade 28 moves into engagement with contact 32.

High voltage power is supplied to the cooling motor In by means of. line wires 35 and 36. Low voltage power is supplied to relay II by means of a step-down transformer 31 which is provided with a high voltage primary 38 that is connected to line wires 33 and 36. The step-down transformer 31 additionally includes-a low voltage secondary 3!. Whenever electromagnetic coil 25 becomes energized to'a sumclentLv greater extent than electromagnetic coil 23 so as to bring contact'blade 28 into engagement with contact 32, electromagnetic coil i2 is energized as follows: secondary 39 of transformer 31, wire 33, wire 30, contact 3|, contact blades 21 and 28, contact 32.

.wire 3|, relay coil |2, wire-33, and wire 32 to the other side of secondary 39. Switch arms 13 and II are thereby moved into engagement with contacts l6 and I1. Engagement of switch arm i3 with contact l3 establishes 'a holding circuit for relay coil i2 which is independent of the contact blade 23 and contact". This holding circuit is as follows: secondary 39, wire33, wire 33, contact 3|, contact blade 21, wire 33, contact l3, switch arm I 3, wire 33, relay coil 2, wire 33, and wire 32 to the other side of secondary 39. Engagement of switch arm I! with contact |1 energlzes the cooling motor in as follows: line wire 33, wire 3!, switch arm i3, contact i1, wire 36, cooling motor l3, and wire 31 to line wire 38. When the energization of electromagnetic coils 23 and 23 is again equalized so as tomove contact blade 28 from engagement. with contact 32, the 56 initial energizing circuit forrelay coil l2 is'interrupted but the relay coil l2 remains energized by the holding circuit described above. However, when the electromagnetic coil 24 becomes more highly energized than the electromagnetic coil 25, then contact 'blade 21 disengages contact 3| and the holding circuit for relay coil I2 is interrupted, whereupon armature l3 and switch arms l4 and I5 return to the position shown in the drawing wherein the cooling motor ill is deenergized.

It isto'be understood that while amarticular type of control system by means of which the balanced relay 25 controls the temperature changer .58 has been disclosed herein, that any other system or means of suitable character could be employed-for this purpose.

The balanced relay 20 is adapted to be controlled by a space temperature variablersistance thermostat generally indicated at 58 which responds to the dry bulb temperature of the space, a space relative humidity responsive variable resistance controller 5|, and an outdoor temperagire variable resistance thermostat or'controller The space temperature variableresistance controller or thermostat 50 is herein shown as comprising a potentiometer thermostat which includes a space or indoor resistance 55 that is adapted to be traversed by a movable contact arm 56. The movable contact arm 58 is controlled by a space temperature responsive thermal v element 51 shown as comprising a bimetallic eleinent having one of its ends secured as at 58 and its other end carrying the contact arm 58. The arrangementis preferably such that thermal element 51 causes the contact arm 56 to move from thecold or left-hand end of indoor resistance 55 to the hot or right-hand end thereof upon a predetermined. variation in space temperature which is herein indicated as comprising a variation of from 75F. to 85 F.. It will be understood that this range of the space temperature responsive thermostat 5ll should be selected to correspond with the desired or permissible fluctuations in the dry bulb temperature of the space.

The relative humidity responsive controller 5| isalso shown in the form of a potentiometer which includes a humidity resistance 80 that is adapted to be traversed by acontact arm 5 I; The contact arm 6| forms one arm of a bell crank.

pivoted at 62 and which includes a second arm 63; The arm 63 is connected to one end of a humidity responsive element .84 herein shown as comprising a plurality of strands of hair, the other ends of which'are fixed as indicated at 85. The proper tension is placed upon the humidity responsive element 64 by a coiled spring 68. The arrangement of humidity responsive controller is such that contact arm 6| moves from the left- I hand end of the humidity resistance 80. to the right-hand end thereof upon predetermined variations. in the space relative humidity which, forthe purposes of this explanation, have been selected ranging from 30% to I The outdoor thermostat orcontroller, includes three resistances 10, 1|, and 12 which are respectively traversed by contact harms I3, 14, and I5,

all of which are mounted upon and secured to a common controlling shaft 16. The, shaft 15 is adapted to be rotated by an outdoor responsive thermal element 11 which is shown as comprising arcoiledbi'metallic strip. One end of this thermal element 11 is fixed as indicated at 18, whereas its other end is connected to the shaft 18. The contact arms 13, I4, and 15 are adapted to traverse completely the resistances 10, II, and 12 upon outdoor temperature changes throughout a range corresponding to the range of outdoor temperature within which it is desired to vary the indoor orv space effective temperature. In this particular embodiment of the invention, this range has been selected to start at 75 F. and end at 100 F., the left-hand ends of resistances 10, II, and 12 being the cold or 75 F. ends, whereas the righthand ends thereof are the hot or 100 F. ends.

Low voltage power is supplied to the balanced relay control system by the secondary 38. of the step-down transformer 31. The relay coils 24 and 25 of the balanced relay 20 are connected in series across the secondary 38 by wires 33, 80, 8|, 82, 83, 84, 85, and 42. The indoor resistance 55 and the humidity resistance 58 of the indoor thermostat 50 and the relative humidity control 5|, respectively, are connected in parallel with each other and are connected in parallel with' the series connected relay coils 24 and 25 through the resistances 12 and Ill by wires 86, 81, 88, 83, 90, and 9|. The contact arms 56 and 6| are connected to each other and to the center of resistance II by wires 92, 93, and 94, and the contact arm 14 is connected to the junction of, or in between, the relay coils 24 and 25 by means of a wire which is connected to the wires 82 and 83. g

With the parts in the position shown, the space relative humidity, the space dry bulb temperature, and the outdoor temperature are all intermediate the ranges of their respective controllers. Contact arm 56 is therefore engaging the center portion of indoor resistance contact arm 6| is engaging the center portion of the humidity resistance 68. tact arms i3, 14, and 15 are engaging the center portions of resistances 10, II, and 12. Equal portions of resistances l8 and 12 are therefore conneoted to their respective electromagnetic coils 25 and 24, and none of the resistance II is in circuit with the wires 94 and 95. The electromagnetic coils 24 and 25 are therefore equally energized so that contact blade 4 contact 3| as heretofore explained.

electromagnetic coils .25 and 24, contact blade 23' 26 is engaging 55, and the will move into engagement-with contact 32,-

whereupon the cooling motor ID will be energized through relay asheretofore explained. The space will therefore besubjected to a cooling effect which .will cause a lowering'in the space temperature and movement'of contact arm 56' along indoor resistance 55 towards the left-hand end thereof. This action will cause a gradual denetic coil 25 and a gradual increase in the voltage drop across electromagnetic coil 24. When the space temperature has thus been lowered sufl crease in the voltage drop across the electromag- I ficiently, electromagnetic coil 24 will become more I highly energized than electromagnetic coil 25, and both contact blades 21 and 28 will move from engagement with their respective contacts 3| and 32 whereupon the cooling motor ill will be deenergized as heretofore explained. In this manner, as long as the outdoor temperature and space relative humidity remain constant, the space dry bulb temperature responsive thermostat will maintain the space temperature within a predetermined range which is dependent upon the prevailing outdoor temperature and space relative humidity.

Assuming that the outdoor temperature still remains constant but that there is an increase in the space relative himidity, then the contact arm 6i will movealong humidity resistance 60 towards the right-hand end thereof. This action will increase the voltage drop across electromagnetic coil 25 and reduce the voltage drop across electromagnetic coil 24 so that the space temperature need not become quite so high before contact blade 28 will engage contact 32 to place the cooling means a in operation. Similarly, if the relative humidity 20. of the space decreases so that contact arm 6| moves along humidity resistance 60 towards the left-hand end thereof, the space temperature must become higher than before in order to cause a sufficient diiference in the voltage drops across 25 electromagnetic coils 24 and 25 to result in engagement of contact blade 28 with contact 32.

In this manner, the prevailing temperature which is maintained by the controller 50 is respectively decreased and increased as'the space rela- 30 tive humidity increases and decreases. By properly proportioning the response and resistance valuesof the space temperature controller 50 and relative humidity controller 5|, the effective tem- 'perature may be maintained within a substantially constant range for any particular outdoor temperature. This phase of the invention has utility for heating as well as for cooling.

If the outdoor temperature should increase, a smaller amount of resistance 10 will be con- 40 nected between the electromagnetic coil 25 and the left ends of resistances 55 and 80, and a larger amount of resistance 12 will .be connected between the electromagnetic coil 24 and the right ends of resistances 55 and 60. This causes a decrease in the voltage drop across electromagnetic coil 25 and an increase in the voltage drop across electromagnetic coil 24. The space temperature must therefore increase to a greater extent before the voltage drop across electromagnetic coil 25 will become greater than the voltage drop across electromagnetic coi124 by the amount necessary to bring contact -.blade 28 into engagement with contact 32. As a result, the effective temperature maintained within the space is increased-as the outdoor temperature increases. Similarly, upon a reduction in the outdoor temperature a larger amount of resistance [0 is placed in circuit with the electromagnetic coil '25, whereas a smaller amount of the resistance 12 is placed in circuit with electromagnetic coil 24 whereby the control of the space temperature I the space humidity controller 5| will be modified in an-opposite manner to lower the effective temperature maintained within the space. By properly proportioning the resistance values of resistances I0 and 12 the magnitude of the effect of the outdoor controller 52 upon the control system a for the balanced relay 2| may be varied as de- 0 sired, In-the preferred embodiment of the invention, the value of these resistances is so selected that the space effective temperature rises at a lower rate than the outdoor temperature. Suitable resistance values forres'istances II and I2 are '10 ohms in a system wherein the resistance controller 50 and values of indoor and humidity resistances 55 and 60 are ohms.

Whenever the outdoor temperature rises above or falls below a value intermediate its total effective range, the contact arm 14 places a variable amount of resistance H in circuit with the wires 93 and 94. This placing of resistance H in this circuit prevents a. complete short-circuiting of either of the electromagnetic coils 24 and 25 when the outdoor temperature, the space, and the space relative humidity reach the proper extremes whereby some current always fiows through the electromagnetic coils 24 and 25 so that the system remains operative under all conditions.

It will be readily apparent that the resistance 1| could comprise a pair of separate resistances instead of being a single resistance having a connection intermediateits ends.

While a specific embodiment of the invention has been disclosed herein, many changes may be made by those skilled in the art without departing from the invention, and I therefore intend to be limited only by the scope of the appended claims.

I claim:

1. In combination, means in control of the conditioning of the air in a space, a pair of series connected electromagnetic coils in control thereof, a space temperature responsive potentiometer having a wide range equal to the desired limits of space temperature variation in warm weather, a space relative humidity responsive potentiometer having a wide range equal to the range of relative humidity within which it is desired to make corrections of the space temperature in order to maintain the effective temperature within predetermined limits, three variable resistances and associated contacts, electrical conductors connecting the low value ends of both thepotentiometer resistances to one end of one of said three resistances, electrical conductors connecting the associated contact of said resistance to one end of one of said electromagnetic coils, electrical conductors connecting the high value ends of both the potentiometer resistances to one end of another of said three resistances, electrical conductors connecting the associated contact of said resistance to one end of the other of. said'electromagnetic coils, conductors connecting the contacts of said potentiometers to the center of said third resistance, conductors connecting the contact of said third resistance to the junction of said electromagnetic coils, means responsive to changes in outdoor temperature in control of the contacts for said threeresistances and arranged to insert less of said first resistance in series with the low value ends of said potentiometers upon outdoor temperature rise, and a source of power connected directly across said series connected electromagnetic coils.

'2. In combination, means incontrol of the conditioning of air in a space, a pair of series connected electrically energizable means in control thereof, a pair of potentiometers including potentiometer resistances and associated contacts, three variable resistances and an associated contact for each of said resistances, conductors connecting one end of a first of said resistances to one end of each oi said potentiometer resistances, conductors connecting one end of a sec- 0nd of said resistances to the other end of each of said potentiometer resistances, conductors connecting one of the contacts of said first and second'reslstances to one end of one of said electrically'energ'izable means and the other of said condition responsive devices including a moisture contacts to one end of the other of said electrically energizable means whereby the two potentiometer resistances, in parallel, are connected in parallel with the series connected electrically energizable means through two of said variable resistances, conductors connecting the contacts of said potentiometers to the center of the third variable resistance and the contact thereof to the junction of the series connected electrically energizable means, three air condition responsive devices including a temperature responsive device and a moisture responsive device, separate connections between two of said devices and the two potentiometer contacts, connections between the third of said devices and the three .variableresistance contacts, said lastnamed connectionsbeing arranged to increase the eifective portion of the'first of said variable resistances while decreasing the effective portion of the second of said variable resistances, and a source of power connected across said series connected electrically energizable means.

3. In combination, means in control of the cooling of a space, a pair of series connected electromagnetic coils in control thereof, a space temperature responsive potentiometer having a wide range equal to the desired limits of space temperature variation inwarm weather, a space relative humidity responsive potentiometer having a wide rangeequal to the range of relative humidity within which it is desired tomake corrections of the space temperature in order to maintain the eifective temperature within predetermined limits, electrical conductors connecting' both of the resistances of the potentiometers in parallel with the series connected coils and the movable contacts of the potentiometers to the junction of said coils, and outdoor temperature actuated variable resistance means associated with said coils for modifying the efiect of said potentiometers thereon in such manner as to increase the effective temperature of the space as the outdoor temperature rises.

4. In combination, means in control of the conditiomof the air in a space, a pair of series connected electrically energizable means in control thereof, a pair of potentiometers including potentiometer resistances and potentiometer contacts, electrical conductors connecting both.

of the potentiometer resistances in parallel with the series connected electrically energizable means and the contacts of the potentiometers to the junction of the series connected electrically energizable means, variable resistance means associated with said electrically energizable means to modify the eflect' of thepotentlometersthereon, a source of electrical power connected to said electrically energizable means, three air responsive device, and separate connections between said three devices and the potentiometer contacts and variable resistance means.

t. .11 combination; a temperature changense- ,ries connected oppositely acting electrical means both potentiometers in parallel in control thereof, 'a space temperature responsive potentiometer having a range equal'to the permissible space temperature fluctuations, a. space relative humidity responsive potentiometer having a range equal to the permissible relative humidity fluctuations, conductors connecting with the series connected electrical means and outdoor temperaturenresponsive variable resistance means associated-with the electrical means for modifying the action of said potentiometers thereon. 7

6. A system of the class described, comprising, in combination, means in control of the cooling of a space, a pair of series connected oppositely acting electromagnetic coils in control of said means, a pair of variable resistances controlled by fluctuations in outdoor temperature connected one to each of the free ends of said coils, a pair of potentiometers connected across said series connected coils through the variable resistances, a space temperature responsive thermal element in control of one of the potentiometers, and a space relative humidity responsive element in control of the other of the potentiometers.

'7. A system of the class described, comprising, in combination, means for controlling the condition of a space, oppositely acting electrical means in control thereof, a space temperature responsive potentiometer in control of the electrical means, a space relative humidity responsive potentiometer for additionally controiling the electrical means, and variable means responsive to outdoor temperatures for modifying the action of said potentiometers on the electrical means.

8; In an air conditioning system, in combination, means in control of the condition of air in a space, a pair of series connected electrically energizable means in control thereof, a pair of control of said electrically enpotentiometers in ergizable means, variable resistance means to modify the action of said potentiometers on the electrically energizable means, three air condition responsive devices including a moisture responsive device, connectionsbetween one of said devices and one of the potentiometer connections between another of said devices and the other potentiometer, and connections between the third of said devices and the variable resistance means.

9. In combination, means in control of the condition of a space, electrical means in. 'control thereof, a variable resistance space temperaresistance I ture actuated controller, a variable resistancetentiometer having a wide range equal to the permissible limits of space temperature variation in warm weather, a space relative humidity responsive potentiometer having a wide range equal to the range of relative humidity within which it is desired to make corrections of the space temperature in order to maintain the effective temperature within predetermined limits, and electrical conductors connecting both of the resista'nces of the potentiometers in parallel withthe series connected coils and the movable contacts 'of the potentiometers to the junction of said coils;

11. In combination, a temperature changer, series connected oppositely acting electrical means in control thereof, a space temperature responsive potentiometer having a range equal to the permissible space temperature fluctuations,'a space relative humidity responsive potentiometer having a range equal to the permissible relative humidity fluctuations and which responds to relative humidity regardless of temperature fluctuations, and conductors connect- 2,101,808 ing both potentiometers to the series connected electrical means including conductors connecting both potentiometer reactance members in parallel with the series connected electrical means.

12. In an air conditioning system, in combination, means to change the condition of air in a space, series connected oppositely acting electrically energizable means in control thereof, a pair of potentiometers having their resistance elements connected in parallel therewith and their contacts connected to the junction of the series connected electrically energizable means, temperature responsive means in control of one of said potentiometers, and moisture responsive means controlling the other of said potentiometers.

13. In an air conditioning system, in combination, means to change the condition of air in a space, oppositely acting electrical means in control thereof and connected in series across a source of power, a pair of variable resistances including movable contact means connected one to each end of the series connected electrical means, a single resistance connecting said variable resistances, a movable contact adapted to traverse the single resistance and connected. to the junction of the series connected electrical means, an outdoor condition responsive device in control of the contact means, and a space moisture responsive device in control of said contact.

means, a moisture responsive device in control of one of said contact means, and a temperature responsive device in control of the other of said contact means.

15. In combination, means in control of the cooling of a space, electrical means in control thereof, a variable resistance space temperature actuated controller, a variable. resistance outdoor temperature responsive controller, a variable resistance space relative humidity responsive controller, and electrical connections connecting all of said variable resistance controllers to said electrical means in a manner to cause an increase in the temperature maintained in said space upon either a lowering in the space relative humidity 01' a rise in the outdoor temperature.

16. In combination, means in control of the condition of a space, electrical means in control conditions.

thereof, a space temperature responsive variable resistance controller having a relatively wide range of response in control thereof and requiring only a portion of its total range of movement to cause a complete change in the operation of 'said cooling means control, and a variable resistance controller responsive to the relative humidity of the space electrically associated with said first-named controller to vary the operating range thereof in respect to its total range in a manner to increase the temperature of the space upon a decrease in the relative humidity thereof.

17. In combination, means in control of the cooling of a space, electrical means in control thereof, a space temperature responsive variable resistance controller having a relatively wide range of response in control thereof and requiring only a portion of its total range of movement to cause a variation in the operation of said cooling means control, a variable resistance controller responsive to the relative humidity of the space electrically associated with said first-named controller to vary the operating range thereof in respect to its total range in a manner to increase the temperature of the space upon a decrease in the relative humidity thereof, and a variable resistance controller responsive to an outdoor temperature condition electrically associated with said first-named controller to vary the operating range thereof in respect to its total range in a manner to increase the temperature maintained in the space upon an increase in the outdoor temperature condition.

nation, means to change the condition of air in a space, electrical means in control thereof, a variable resistance space relative humidity resp'onsive controller, a variable resistance outdoor temperature responsive controller, and electrical connections connecting both of said variable resistance controllers to the electrical means for.

controlling the condition of the air in the space in accordance with space relative humidity conditions and outside temperature conditions.

19. In an air conditioning system, in combination, means to change the condition of air in a space, electrical means in control thereof, a first variable control resistance means, means responsive to variations in space temperature for operating the first variable control resistance means, a second variable control resistance means, means responsive to variations in space relative humidity for operating the second variable control resistance means, and electrical connections connecting both of said variable control resistance means to the electrical means for controlling the condition of the air in the space in accordance with the space temperature and relative humidity LEWIS L. CUNNINGHAM. 

